Impacts of Climate Change on Regional
Climate in Taiwan and Southeast Asia
Jau-Ming ChenProfessor, Department of Maritime Information andTechnology
National Kaohsiung University of Science andTechnology, Taiwan

International Seminar of UNESCO Chair Project, Oct. 2, 2021

Topics:
1. Present State of Global Warming
2. Impacts of Global Warming and Urbanization on Taiwan
3. El Niño impacts on Southeast Asia under Global warming2

Topic 1:
Present State of Global Warming3全球年均溫
Global surface
temperature

1920-20191970-2019

1.5

1970-2019
warming trend= 1.9oC/100 yr

1920-2019
warming trend= 1.0oC/100 yr

10.5°C

0-0.5-1
1920

1940

1960

 Continuous warming Warming is getting faster

年
year

1980

2000

2020

4

4 stair-like warming stages
separated by 3 suddenly-warming years
全球年均溫
Global surface
temperature

1920-20191970-2019

1.5
1

2

10.5°C3

4

0-0.5-1
1920

1940

 Four stages:
 Separated by1960

年
year

1920-1976

1980

2000

2020

1977-1997
1998-2015 2016-present
1976-77
1997-98
2015-16

5ENSO Index
1997-98

2015-16

1976-77

El Niño: positive value >= 0.5oC
La Niña: negative value <=-0.5oC

3 suddenly–warming years correspond to 3 El Niño events.

6

Story of UN IPCC
(Intergovernmental Panel on Climate Change)
To summarize and report the present states andfuture projections of climate changeFirst Assessment Report(AR1): 1990
Second Assessment Report (AR2): 1995
Third Assessment Report (AR3): 2001
Fourth Assessment Report (AR4): 2007
Fifth Assessment Report (AR5): 2014
Sixth Assessment Report (AR6): 2021 (Aug.)7

During early 1990s, the releases of AR1 and AR2 werestrongly challenged by scientific community.
Questions raised at that time: What is “global warming”? (It is a new concept) Is it strong and fast enough to affect us?
 What is wrong for using cheap gasoline and coal?
 Can it continue on?
 Is it a part of the natural oscillation of climate system?

8

Natural Oscillation
Pacific Decadal Oscillation: around 20-30-year oscillations
1980-1997: positive phase
1998-2019: negative phase
PDO phase changes from positive to negative around late 1990s,
but temperature continues to increase, rather than decrease .

9

1997-98 El Niño event results in a record-breaking annual-mean temperature in 1998.
Afterwards, temperature stays at the high level during the third stage.
Warming exists and continues.
This is the main reason to stop questions about the existence of global warming .
全球年均溫

1920-20191970-2019

Warming
is not affected by natural variability, but by man-made forcing.
1.5
Global surface temperature
10.5°C

0-0.5
-1
1920

1997-98
1940

1960

1980

2000

2020

年
year

10

After 1997-98 El Niño event, AR3 in 2001 and AR4 in 2007 haveattracted major attentions from the world.
In 2007, IPCC and Al Gore Jr. (former vice present of USA, Authorof “An Inconvenient Truth”) were awarded of the Nobel Peace
Prize.
“For their efforts to build up and disseminate greater knowledge
about man-made climate change, and to lay the foundations for themeasures that are needed to counteract such change".

11

The current warming states reported by AR6 (released in Aug. 2021)
 Human-induced climate change is already affecting many weather
and climate extremes in every region across the globe.
 Hot extremes (heatwaves) and heavy precipitation have become
more frequent and more intense.
 Monsoon precipitation increases after 1980s due to increased
greenhouse gases (GHG).
 With the radiative forcing induced by current GHG concentration,
the equilibrium climate sensitivity is estimated to have atemperature rise of 2.5o-4oC.

12

Projection of future climate

Adopted from IPCC AR6 WGI

weak emission

strong emission
With respect to the mean temperature of 1850-1900.
 2001-2020 was 0.99oC higher than 1850-1900.
 2030 and 2050 are likely to be 1.5oC and 2.0oC higher than 1850-1900, respectively.
SSP: Shared Socio-economic pathway

13

IPCC AR6: Many changes due to past and future greenhouse gasemissions are irreversible for centuries to millennia, especiallychanges in the ocean, ice sheets and global sea level.
CO2 tends to resolve in cold waters like carbonated drink (Coke)
Oceans are the major sink of CO2:
1. Ocean absorbs CO2 acidification
2. Increased GHG  global warming  higher water temperature reducing ocean’s capability in absorbing CO2
 GHG concentration increases in the atmosphere Stronger global warming
 higher temperature in ocean waters
Positive feedback process
Self-intensification process

14

Melting of Arctic sea ice
Incoming solar heating:white sea ice : 90% reflection, 10% absorption
blue sea water: 10% reflection, 90% absorption
Global warming Higher temperature in air and sea waters
 more melting of Artic sea ice
 More sea waters exposed to Sun
 More absorption of solar heating by sea water Higher temperature in sea waters
 more and faster melting of sea ice
Serious consequence
Arctic sea ice: to cool the Earth by reflecting back solar heating
Arctic sea water: to heat the Earth by absorbing solar heating
 Faster warming

positive
feedbackprocess15

Points for attentions: Global warming process seems to be irreversible with
its impacts getting stronger from now on.
 Climate refugees may escape from unbearable
environments in the near future.

16

Topic 2:
Impacts of Global Warming andUrbanization on Taiwan

17Signature of global warming over Taiwan:
persistent warming trends over every sectors of Taiwan
TaipeiTaichung

Annualmean T

HualienTainanReference:
J.-M. Chen (2006)
Climate Variability

18

Urbanization effecturban: ●suburban:

Penchiayu(population: 100)
Taipei(population: 2.6M)

Fall temperature in Taiwan
strongwarming

weakwarming

Stronger warming trend in urban region than suburban region.
 Difference caused by urbanization effect.
Reference:J.-M. Chen et al. (2007), TAO

19

1970-2019 warming trend
Taipei:3.37oC/100 yr
Penchiayu: 1.33oC/100 yr
Global mean: 1.9oC/100 yr
Annual-mean temperature

TaipeiPenchiayu

Faster warming in Urban region than suburban region201970-2019 warming trend
Taipei:2.76oC/100 yr
Penchiayu: 1.33oC/100 yr
Annual-mean daily maximum temperature

TaipeiPenchiayuWarming of day-time temperature

21

1970-2019 warming trend
Taipei:
4.06oC/100 yr
Penchiayu: 1.73oC/100 yr
Annual-mean daily minimum temperature

TaipeiPenchiayu

Warming trend of night-time temperature is larger thanthat of day-time temperature. Why?

22

Day time

Night time

Figure Source:
NationalInstitute ofWater andAtmosphericResearch

Sun’s surface (~6000oC): solar radiation  high energy  short wave
Earth’s surface (~15oC) : earth radiation  low energy  long wave

23

Greenhouse gases only absorb long wave, but not short wave.
Day time: half of solar radiation penetrates atmosphere to heat the Earth.
Night time: Earth radiation releases heat back to atmosphere Partial long-wave radiation is absorbed by GHGs to warmatmosphere Without greenhouse effects, Earth’s surface temperature is expected
to be around -19oC, not current 15oC.
More GHGs  more absorptions during night time to directly increase night-time temperature the remaining heat to indirectly increase day-time temperature
Warming trend in night time is larger than day time.

24

The long-term impact of CO2The major component of GHGs is CO2 .
 Once existence, CO2 can exist in nature for 60-100 years.
 Even without any more GHG emission from now on, the current
warming state needs 60-100 years to gradually decrease.
 It needs to plant a tree with a life time longer than 60 years toefficiently reduce CO2 concentration.

25

Urbanization effect

When solar heating reaches Earth’s surface:
Urban region:roads and buildings absorb solar heating in day time and release it
back to atmosphere in night time
 processes to heat the city  heat-island effect
Suburban region:
solar heating can be absorbed by waters on surface or underground heating changes water into water vapor via evaporation
 water vapor rises into the sky to form cloud and release heating
into the upper-level atmosphere cloud causes rainfall to cool the surface
 processes of afternoon thunderstorm
 pay attentions to reductions of thunderstorm over urban regions

26

Urbanization effects in Taiwan(population)
Urban

SuburbanUrban/Suburban

Taipei (2.6M)
Taichung (2.8M)
Tainan (1.9M)
AveragePenchiayu (0.1K)
Jihyuehtan (15K)
Lanyu(5K)
Average1970-2019
warming trend ofannual-mean T
3.37°/100 yr
3.18°/100 yr
2.21°/100 yr
2.92
1.33°/100 yr
0.77°/100 yr
0.66°/100 yr
0.92
3.17

Urban warming is about 3 times larger than suburban warming.
2.92oC (total warming) = 0.920C (global warming)+ 2.0oC (urbanization effect)27

1970-2019 trend
Taipei: 3.33oC/100 yr
Maximum temperature in each year
Taipei

Before 2000: in the range of 35.5-38.5oC
After 2000: in the range of 36.5-39.5oC

28

1970-2019 trend
Taipei: 7.53oC/100 yr
Minimum temperature in each year
Taipei

In 2017 and 2019, daily temperature was never lower than 10oC
 No cold surge in Taiwan for these two years.
 Longer summer with shorter or no winter29

Points for attentions: For the metropolitan areas in the populous Asia,
a longer summer with a shorter or no winterwill appear in the near future More energy is needed to cool people for theirsurvival from the abnormal warming environments.

30

Topic 3:
El Niño impacts on Southeast Asia
under Global warming31

Cold upwelling in the tropical eastern PacificCold water was driven westward by tropical trade (west-bound) winds
Heated by sun, waters are warmer as they move more westward
Tropical Pacific: warm in the west and cold in the east

Normal climate state
sea surface temperature

upwelling32

Warm water in the west heats airs to rise upward motion of water vapor  cloud  rain
Cold water in the east cools airs to sink downward motion  no cloud  no rain
Rain forests exist in Southeast Asia around the tropical western PacificWarm West – Cold East
Regular climate statesea surface temperature

upwelling33

El Niño event
The occurrence of anomalous westerly (east-bound) flows to drive warm watersfrom the tropical western Pacific toward the central and eastern Pacific More surface waters flow into the tropical eastern Pacific Upwelling is blocked  less cold water from deep sea into surface
 Surface waters becomes warmer in the tropical eastern Pacific (Warm Event) The leaving of warm water makes the western Pacific colder
 Colder in the West – Warmer in the East

El Nino event

34

La Niña event
The enhancement of tropical trade winds (west-bound) More warm waters gather in the tropical western Pacific The leaving of water from the eastern Pacific Enhanced upwelling cools the eastern Pacific (Cold Event) Surface waters becomes warmer in the western Pacificand colder in the eastern Pacific Warmer in the West – Colder in the East

La Nina event

35

Climate state:
El Niño:La Niña:Sea Surface Temperature
western PacificEastern Pacific
warm
cold
becomes colder
becomes warmer
becomes warmer
becomes colder

El Niño tends to induce a variability state opposite to the climate state Colder waters in the western Pacific induce downward motions
 Reduced clouds and rains over the SE Asia
 Likely to have a dry condition during an El Nino event.
La Niña tends to induce a variability state enhancing the climate state More clouds and rains over the SE Asia

36

ENSO Index

1997-98

2015-16

1976-77

El Niño: positive value >= 0.5oC
La Niña: negative value <=-0.5oC

1997-98 El Nino event37

1997-98 El-Niño event: drought first and forest fire next

The 1997 group of forest fires in Indonesia that lasted well into 1998 wereprobably among the two or three, if not the largest, forest fires group in the lasttwo centuries of recorded history. (From Wikimedia Commons)Countries affected
Indonesia
Singapore
Malaysia
Thailand
BruneiVietnamPhilippines
Sri Lanka

Smoke and ozone pollution from Indonesian forest fires, 1997
(photo from NASA)38

Why is El Nino event important for SE Asia?
90N

World-T2m

DEC9-DEC0(JJA)
3.5

4 5

35
4 4.5
2.5
42
2.5
360N
3.5
45N 5
4.5
4 3.5
3 34330N
344 4.52.515N
3.575NEQ

3.5
4

15S30S

1.545S60S

275S
90S
0E

2.5
2.5 2

3 2.5

2.5
1.5

230E

3

4.5 5

2.560E

3

2.5 2

3

2.5
3 2.5
2
3
390E

120E

3.5
4.5

3 2

1.5
2150E

180

2.5

2.5
12150W

3
2.5

4

2.5
2.5

2.5
2.5

1.5
3
43.5

3.55

modelm-a1b3 3
3.53.5

3

4.5

2
1 1.5
35

24
3.5
2.5
4

1.5 4

4
3.5
3
2.5

3
3.5
225

2

1.5

1.5
122
1.5120W

90W

360W

3.5 4.54330W

0.500

Future change [(2090-2100) – (2000-2010)] of surface temperature projected by IPCC AR4
Major features:
 Overall warming around the globe.
 More warming in the polar regions than the tropical regions.
 More warming in the eastern Pacific than the western Pacific.
(Additional heating transfers toward the colder regions first)

39

Sea Surface Temperature
Global warming:
El Niño:western Pacificless warming
becomes colder

Eastern Pacificmore warming
becomes warmer

Variability features of surface temperature in the tropical Pacifictend to be in phase between El Niño and global warming Their double impacts act to enhance drought conditions in
the SE Asia during an El Niño event.
 To cause a higher temperature rise during an El Niño year
under global warming
El Niño  a warm event  to cause a temperature rise
 more warming
La Niña  a cold event  to cause a temperature decreaseless warming40Points for attentions: The occurrence of another strong El Niño event mayraise global temperature to another higher stage.
 Higher temperature speeds up water evaporation.
 A better chance causes an agricultural drought.
 Water resources are getting more importantto secure people’s living in the future.

41

Summary: Be prepared for faster global warming andmore hazardous weather and climate impacts.
 More energy powers will be needed to cool themetropolitan regions.
 Heatwaves and droughts will occur more frequently
with stronger intensity to affect agricultures and ourdaily life, particularly for SE Asia during El Niño years.
42Thanks for your attentions!

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